Defect engineering of oxygen vacancies in SnOx electron transporting layer for perovskite solar cells

In this work, we present the self-passivation of tin oxide (SnOx) electron transporting layer (ETL) induced by manipulatively filling the oxygen vacancies for perovskite solar cells (PSCs). The oxygen component of SnOx ETL is tuned by the annealing under the oxygen (O2) atmosphere to control the trap state density for high electron collection efficiency. With increasing the O2 content when annealing, oxygen vacancies of SnOx ETL are filled gradually, with the x of SnOx being up to 1.84, while the crystalline structure grown better to be rutile. Furthermore, the measurement of electron transport dynamic demonstrates that the SnOx ETL is benefit for electron collection after O2-annealed, and receiving high power conversion efficiency (PCE) of PSCs. The PSC based on the O2-annealed SnOx ETL yields an average PCE of over 19%, much higher than 17.81% of that after N2-annealing. The O2-annealed PSC gives a champion PCE of 20.40%, with a short current density of 24.41 mAcm−2, an open circuit voltage of 1.14 V and a fill factor of 73.37%. Therefore, the annealing is an efficient and simple way to control the quality of SnOx ETL for the high performance PSCs.